Breastfeeding contributes to maternal to child transmission of HIV, which is responsible for 90% of the 800,000 HIV infections that occur each year among the world's children, the vast majority of which are in sub-Saharan Africa. Current UNICEF/WHO recommendations focus on the challenge of making breastfeeding safer; guidelines include heat treatment of breastmilk as an official infant feeding recommendation for HIV positive mothers in developing countries. This study will evaluate nutritional and bacteriologic safety of home pasteurized breastmilk. This information is necessary to adequately inform mothers of risks and benefits of this feeding alternative. The overall objective of this study is to scientifically evaluate the effect of Flash-heat (a method mothers can perform at home to inactivate HIV) on nutrient, immunologic and anti-infective components of breastmilk. Heated milk must be nutritious enough to support growth and development, retain anti-infective activity in order to prevent infectious morbidities. Specific aims include evaluation of impact of Flash-heat on the following aspects of breastmilk samples from HIV-infected mothers: 1) vitamin content and protein digestibility; 2) key bioactive proteins (immunoglobulin A, lysozyme and lactoferrin); 3) antibacterial activity. Specific aim 3 is to determine dietary needs of African infants of different ages receiving heat-treated milk. 50 breastmilk samples have been previously collected from South African women who are HIVpositive, and Flash-heated. In the available aliquots of heated and unheated milk we will measure and compare: a) concentrations of vitamins A, ascorbic acid, thiamine, riboflavin, pyridoxine, folate and B12, known to be relatively heat-sensitive; b) concentration and digestability of proteins lysozyme and lactoferrin; c) concentration of total and slgA and bioactivity (via binding) of each against specific antigens (measles, S. pneumoniae, influenza); d) bioactivity of isolated anti-infective proteins lactoferrin and lysozyme, via uptake into cells, enzymatic and bactericidal activity; e) antibacterial properties of milk via inhibition of growth of E. coli and S. aureus over time. Information from these analyses will be used in linear programming to predict how the described changes in nutrient content of milk due to heating would affect the overall dietary needs of the child and the associated costs.